Free lift truck



J. E. OLSON FREE LIFT TRUCK Dec. 1, 1959 3 Sheets-Sheet 1 Filed 001;. 31, 1955 IN V EN TOR.

JOHN E. OLSON ATTORNEYS J. E. OLSON FREE LIFT TRUCK Dec. 1, 1959 3 Sheets-Sheet 2 Filed Oct. 31, 1955 INVENTOR.

JOHN E. OLSON ATTORNEYS J. E. OLSON FREE LIFT TRUCK Dec. 1, 1959 3 Sheets-Sheet 3 Filed Oct. 31, 1955 INVENTOR. JOHN E. OLSON BY W A TTORNEYS Unite States Patent FREE LIFT TRUCK John E. Olson, Portland, Greg, assignor, by mesne assignments, to Hyster Company, a corporation of Nevada Application October 31, 1955, Serial No. 543,822

10 Claims. (Cl. 187-9) This invention relates to lift trucks.

In the copending application of Leslie G. Ehmann entitled Lift Truck, Serial No. 459,492, filed September 30, 1954, a lift truck is disclosed having a single mast of tubular form instead of the conventional double-channeled wide mast arrangement. In this truck, there is a limited amount of free lift, that is, elevation of a load carriage Without extension of the mast.

It is a main object of the present invention to provide a truck of the general character disclosed in the abovementioned application, but having a full or 100 percent free lift feature.

It is another object of the invention to provide such a truck in which there is a minimum of angular wobble permitted between the load carriage and the mast when the load carriage is in its lowered position.

Another object of the present invention is to provide such a truck having a novel free lift cylinder especially adapted for but not limited to use with lift trucks having a single tubular mast.

Still another object is to provide a novel free lift cylinder which is less expensive than prior cylinders.

A further object of the invention is to provide a lift truck having two uprights and a novel arrangement for transferring the carriage from one upright to the other. The lift truck of the present invention is characterized by including a fixed outer tubular upright and an inner upright unit telescoped therewithin. A load carriage is moved by a cylinder unit along the outer upright to the upper end thereof without extending the mast and then onto the inner upright unit, whereafter the inner upright unit and the carriage are elevated upwardly together. Various other objects of the present invention will be apparent from the following description taken in connection with the accompanying drawings, wherein:

Fig. 1 is a perspective view of a lift truck embodying the concepts of the present invention, showing the carriage in its lowered position;

2 is a vertical sectional view through the mast taken in the direction longitudinally of the truck, showing the load carriage in its lower position;

' Fig. 3 is a view similar to Fig. 2 but showing the carriage as having been elevated to the upper end of the outer upright;

Fig. 4 is a view similar to Fig. 3, but showing a further stage in the elevation of the carriage;

Fig. 5 is a view similar to Fig. 4, showing a still further stage in the elevation of the carriage;

' Fig. 6 is an enlarged vertical midsectional view through the cylinder unit of the mast;

Fig. 7 is a top view of the cylinder unit taken in the direction of the arrows 7-7 in Fig. 6;

Fig. 8 is a sectional view taken along line 8--8 of Fig. 6;

' Fig 9' is a sectional view taken along line 9-9 of Fig. 6;

' Fig. 10 is a side view of the upper portion of the mast; Fig; 11 is a fragmentary view taken along line 11-11 2,915,144 Patented Dec. 1, .1953.

of Fig. 2, showing a latching arrangement, the uprights 7 parts in Fig. 4; and

Fig. 13 is a view generally similar to Fig. 11 but showing the parts in the same stage of operation as are the parts in Fig. 5.

General description Referring to Fig. 1, the truck 11 carries a single mast at its forward end, the mast including a tubular outer upright 13 of rectangular cross section mounted at its lower end for tilting movement relative to the truck I under the control of a pair of cylinders 15. Movable along the outer upright 13 is a load carriage 17 which is elevated by chains 19 which are operated by a cylinder unit disposed within the mast.

Specific description Referring particularly to Figs. 1 and 2, the outer mast 13 is shown as being fixedly mounted on a base 31, the base having fixed thereto a pair of spaced apart mounting plates 33 which are journaled on the front axle housing 35 of the truck. The tilt cylinders 15 are connected to the upper ends of the mounting plates 33. Thus the mast may be tilted about the axis of the front, axle by operation of the tilt cylinders.

The carriage 17 includes a pair of fork arms 41 and a pair of rearwardly extending spaced apart mounting members 43 which straddle but are spaced from the outer upright 13. The mounting members 43 are connected together at their rear ends by a spacer 45 (Fig. 2), and a roller 47 is rotatably mounted on a shaft fixed to the members 43, the roller rollingly engaging the rear face of the outer upright 13. The carriage includes a front roller 49 also mounted on a cross shaft fixed to the members 43 and rollingly engaging the front face of the outer upright 13 at a level below that of roller 47.

A latch 51 is pivotally mounted at 52 on a crosspiece 53 on the carriage for a purpose to presently appear. A spring 54 urges the latch clockwise, as the parts are depicted in Fig. 2, into engagement with the front face of outer upright 13.

The chains 19 are'each anchored to the crosspiece 53 at one of their ends, and are trained over various other parts in a manner presently to be explained.

Within the outer upright 13 is movably and telescopi cally arranged the inner upright 61, which also is of rectangular cross section. The inner upright is provided at its lower front portion thereof with a shoe 63 for slidable engagement with the opposed inner surface of the outer upright and has a pair of rollers 65 at the lower rear portion thereof for rolling engagement with the op-' an elongated cylinder of approximately the same length as that of the inner and outer uprights and bears at its lower end in a centering recess formed in plate 31. Hydraulic fluid may be supplied to or exhausted from this inner member through a hydraulic line 72.. SlidablY arranged on the upper portion of the inner member 71;

3 is an intermediate member in the form of a cylinder 73' (Fig; 6) carrying a block 75 on its lower'end'. Slidably mounted in surrounding relation to the intermediate cylinder 73. is an outer member 77 in the form of a cylinder which is rectangular in exterior cross section and slidably fits within inner upright 61'. The outer cylinder 77 is longitudinally grooved at 78 (Fig; 9) to accommodate chains 19.

The outer cylinder 77 and the intermediate cylinder 73 have stops 79 and 80, respectively (Fig. 6), to limit. downward movement of the intermediate cylinder relative to the outer cylinder, and the intermediate cylinder 73 and the inner member 71 are provided with stops 81 and 82, respectively, to' limit upward movement of the intermediate cylinder relative to the inner member. Suitable packing, as shown, is provided for the outer and intermediate cylinders.

A head. is fixed on the upper end of the outer cylinder 77, thehead including a baseplate 91 (Fig. 6), four upstandingplates 93 (Fig. 7 a rear plate 95 (Fig. 6), and a front plate 97'. It is apparent from Fig. 2 that the head projects rearwardly beyond the confines of the outer cylinder 77 an extent such that the rear face of the rear plate 95 is flush with the rear face of the outer upright 13. for a purpose to appear presently.

Rotatably mounted on the head and between the plates 93 is a front sheave 1631 (Figs. 2 and 7) and a rear sheave 102 for each of the chains 19. The front sheaves 101 are so located that the chains 19 are disposed just forwardly of the. front face of the outer upright 13. The rear sheaves. 192 are so located that the chains 19, extending downwardly therefrom, pass into the confines of the. inner upright. 61, the chains being then trained over sheaves 195 carried by the. block 75 and then extend upwardly and are anchored to the lower end of the outer cylinder 77.

The operation of the apparatus is as follows. When hydraulic fluid is supplied to the inner member 71 through line. 72, it passes upwardly to the inner member and through ports 1497 (Fig. 6) where it may act on the intermediate and outer cylinders 73 and 77. The diameters of inner member 71 and cylinders 73 and 77 are proportioned so that the intermediate cylinder will move downwardly instead of the cylinders 73 and 77 moving upwardly in unison, or instead of cylinder 77 moving upwardly alone. The particular chain and sprocket arrangement shown provides a two-to-one mechanical advantage in favor of upward movement of cylinders 73 and 77 over downward movement of cylinder 73. Thus the effective area of cylinder 73, that is the area of the annulus between the inner surface of cylinder 77 and the outer surface of member 71, must be more than twice the area of member 71 in order to obtain the desired movement, and such is. the case.

Downward movement of intermediate cylinder 73 from the position shown in Fig. 2 to the position shown in Fig. 3, will function to elevate the load carriage from the Fig. 2 position to the Fig. 3 position at which time the rear roller 47 moves onto plate 95.

At. the same time, the latch 51 snaps overagainst and catches-on an element 108 to lock the carriage relative to the cylinder 77 in the Fig. 3 position.

At this time, the stops 79 and 80 (Fig. 6) engage and thus continued application of hydraulic pressure through line. 72 causes the outer cylinder 77 to move from the Fig 3 position to the Fig; 4 position. During this movement, the intermediate cylinder and the outer cylinder move upwardly in unison and thus the roller 47 remains in; engagement with plate 95.

Movement of the parts to the'Fig. 4 position brings the front roller 49: into engagement with a stop 111 on the olfset portion 68 of the inner upright so that the front roller 49 is retained in engagement with such portion, and a complete transfer of. the carriage from the outer. upright tov theinner upright. andthe. outer cylinder 77 is effected. Stop 111 is laterally displaced from the line of travel of latch 51 so that the two do not come into engagement.

Further upward movement of cylinders 77 and 73 relative to inner member 71 can take place only by raising the inner upright 61 which occurs to extend the mast such as to the Fig. 5 position. Thus the mast may be fully extended.

When fluid is exhausted from line 72 and thus from the cylinder unit, the inner upright 61 will telescope within the outer upright 13 until the parts reach the Fig. 4 position. Further exhaust of the fluid pressure will cause the load carriage 17 and outer cylinder 77 to move downwardly together to the Fig. 4 position, at which time a camming edge 113 on latch 51 will engage the offset portion 68 of inner upright 61 to unlatch the carriage 17 from the cylinder 77. Thus the carriage may move downwardly along the outer upright at the same time that the intermediate cylinder 73 is forced upwardly into the outer cylinder 77 to bring the carriage back to its lowermost position. There is sufficient play between the latch 51 and element 111% to permit the latch element and load carriage to move downwardly a suflicient distance so that the latch may cam itself outwardly free of element 108.

it is apparent from the above description that the carriage can move from the Fig. 2 position to the Fig. 3 position without extension of the mast, so that a full or 160 percent free lift is obtained. When the carriage is raised from the Fig. 3 position to the Fig. 4 position, the outer cylinder 77 is projected upwardly, and since this cylinder slidably fits within the inner upright 61 and takes the forward thrust of the load carriage in the upper positions thereof, the outer cylinder functions as a part of the mast as well as part of the cylinder unit. In fact, outer cylinder 77 and inner upright 61 may be considered as an inner upright unit. Furthermore, the outer cylinder may be considered as a transfer member since it is a part employed in transferring the load carriage from the outer upright to the inner upright unit.

Although the part are designed to achieve the sequence above enumerated, in practice foreign substances collect on the moving parts of the cylinders even though they are normally protected within the confines of the mast. In order to insure the attainment of the sequence desired, a pair of latch devices is provided. These devices are similar and thus only one will be described.

Referring to Fig. 11, a latch device includes a ball 121 which projects into a hole 123 in the outer upright and fits within a hole 125 in the inner upright 61 to releasably lock the inner and outer uprights together against relative movement. Hole 123 is slightly smaller than the ball 121 whereas hole 125 is larger.

.When the outer cylinder 77 moves upwardly from the Fig. 3 position and reaches the Fig. 4 position, a recess 127 (Figs. 11 and 12) in this cylinder is brought into register with the ball 121'. Since further upward movement of the carriage from the Fig. 4 position can only be accompanied by upward movement of the inner upright 61, this upward movement operates to-cam the ball 121 out of the hole 123 in the outer upright and partially mto the recess 127 in the outer cylinder. This functions to latch the outer cylinder 77 to the inner upright 61 and prevents relative movement therebetween.

As the upper end of inner upright is projected upwardly beyond the outer upright, the ball 121 is exposed and to prevent dislodgment of the ball from its place, a latch member 129 (Fig. 1.0) is provided and is pivoted 131 on the inner upright 61 and normally is accommodated within a notch formed in the upper part of the outer upright 13.

A. camming element 133 is provided on the outer upright in operative association with the latch member 129 so that as the inner upright is raised relative to the outer upright, latch member. 129 is cammedv around to. aposition (Fig.- 13) to prevent dislodgment of the ball '121 from its position in engagement with the inner upright 61 and the outer cylinder 77.

Upon downward movement of the parts, the latch member 129 will once again be engaged by the camming element 133 so that the latch member is cammed around to its initial inoperative position. When the parts reach the position shown in Fig. 4, the ball will be in register with the hole 123 in outer upright and since the outer cylinder 77 tends to move downwardly under the weight of the load carriage and its own weight, this force earns the ball 121 out of recess 127 and partially into the hole 123 in the outer upright thus locking the inner and outer uprights together.

With the truck of the present invention, remarkable visibility is attained because of the single tubular mast, and the advantages of 100 percent free lift are also attained. Thus the truck can beoperated to stack or remove loads in places having low ceilings such as box ears, sheds, or similar places. The single tubular mast is very compact since the free lift cylinder unit comprises only three members. "It is also pointed out that there is a minimum of lateral wobble between the carriage 17 and the mastwhen the carriage is in its normal lowered load-carrying position because the carriage engages the puter upright,'which is fixed to base 31, instead of engaging'a'movable'upright as is conventional practice.

Having described the invention in what is considered to be the preferred embodiment thereof, it is desired that it be understood that the invention is not to be limited other than by the provisions of the following claims.

I claim:

1. A lift truck mast assembly comprising inner and outer telescoped uprights, a load carriage movably engaging the outer upright, means for raising said load carriage along the outer upright and beyond the upper end thereof and for raising the inner upright upwardly to a position to project the upper end thereof beyond the outer upright, and means carried by said inner upright for receiving said load carriage from said outer upright, the last-named means having surfaces forming a continuation of the surfaces of said outer upright so that said carriage engages said last-mentioned means in the same manner as it engages said outer upright.

2. A lift truck mast assembly including an outer upright and an inner upright unit telescoped within the outer upright, the'inner upright unit being movable upwardly relative to the outer upright, a load carriage movably engaging the outer upright, said inner upright unit having portions projecting above the outer upright and providing surfaces forming an extension of the surfaces of the outer upright which are engaged by said load carriage, and means for elevating the load carriage along the outer upright and onto said projecting portions and then for elevating said upright unit and said load carriage in unison relative to said outer upright.

3. A lift truck including inner and outer telescoped uprights, the inner upright being movable upwardly relative to the outer upright, a load carriage carrying spaced upper and lower elements in movable engagement with said outer upright, a transfer member telescopically engaging the upper end of said inner upright, and means for moving said load carriage upwardly along said outer upright from a lower position to an upper position at which the upper element of said load carriage engages said transfer member, said means being operable to then move said transfer member and load carriage upwardly in unison while maintaining said uprights stationary until the lower element on said load carriage engages said inner upright, said means being operable to then elevate said inner upright and said load carriage and said transfer member upwardly in unison.

4. A lift truck including inner and outer telescoped uprights, the inner upright being movable upwardly relative to the outer upright, a load carriage carrying spaced upper and lower elements in movable engagement with' said outer upright, a transfer member telescopically said inner upright and said load carriage and said transfer member upwardly in unison, and means for latching said transfer member to said inner upright after the lower element on said load carriage engages said inner upright.

5. A mast assembly comprising a fixed outer tubular upright, an inner tubular upright telescoped within said outer upright and having an upper portion exposed at the front of the assembly, said portion having a front face lying generally in the plane of the front face of 'the outer upright, a ram within said inner upright having a ram part slidably received by the inner upright, 'said part having an upper head portion exposed at the back of said assembly and presenting a rear face lying generally in the plane of the rear face of the outer upright, a load carriage movable along said outer upright and having upper rear roller means and lower front roller means, -means connecting said carriage to said ram to cause said carriage to be elevated upon operation of said ram to place said rear roller means in engagement with said head part, said ram then being operable to elevate said ram part and said carriage in unison to bring said front roller means into engagement with said upper inner upright portion, said ram then being operable to elevate said carriage, ram part and inner upright in unison, with said carriage mutually supported in a horizontal direction by said ram part and said inner upright.

6. A mast assembly comprising a fixed outer tubular upright, an inner tubular upright telescoped within said outer upright and having an upper portion exposed at the front of the assembly, a ram within said inner upright having a ram part slidably received by the inner upright, said part having an upper head portion exposed at the back of said assembly, a loadcarriage movable along said outer upright and having upper rear upright engaging means and lower front upright engaging means, means connecting said carriage to said ram to cause said carriage to be elevated upon operation of said ram to place said rear means in engagement with said head part, said ram then being operable to elevate said ram part and said carriage in unison to bring front means into engagement with said upper inner upright portion, said ram then being operable to elevate said carriage, ram part and inner upright in unison, with said carriage mutually supported in a horizontal direction by said ram part and said inner upright.

7. A mast assembly comprising a fixed outer tubular upright, an inner tubular upright telescoped within said outer upright and having an upper portion exposed at the front of the assembly, an elongated member slidably received by the inner upright, said member having an upper head portion exposed at the back of said assembly, a load carriage movable along said outer upright and having upper rear roller means and lower front roller means, means for elevating said carriage to place said rear roller means in engagement with said head part, said means then being operable to elevate said member and said carriage in unison to bring said front roller means into engagement with said upper inner upright portion, said means then being operable to elevate said carriage member and inner upright in unison, with said carriage mutually supported in a horizontal direction by said member and said inner upright.

8. A lift truck mast assembly including inner and outer telescoped uprights, said outer upright being fixed unit said: inner: upright being movable, a load-carriage Having rear upper roller means and lower front roller meansmovably engaging said outer upright; means for raising said load carriage along the outer upright and beyond the upper end thereof and for raising the, inner upright" upwardly to a position to project the upper portion thereof beyond the upper end of the outer'upright, and means carried by said inner upright: for receiving said loadi carriage from said outer upright, thelast-named means having surfaces forming a continuation of at least the front and rear surfaces of said. outer uprightso that said. carriage: roller means engage said last=named means in a. manner similar to the manner said carriage: roller means engage said outer. upright;

9t Arlift truck mast assembly including an outer uprightand.aninner'upright'unit'telescoped within said outer upright, said. inner uprightunit being movable upwardly relative to said outer upright, a load carriage having upper: rear roller means and lower front roller means movably engaging said outer upright, said inner upright unitliaving portions projecting above said outer: upright and providing surfaces formingan extension of. at least the front and rear surfaces of .said outer upright, and means for elevating said load carriage along said outer upright and onto said projecting portions and then for elevating said inner upright unit and said load carriage in unison relative to said outer upright.

10. A lift truck mast: assembly including as; outer upright and an inner-upright unit teleseoped within said outer upright, said inner uprightunit being' inovableupwardly relative to said outer upright, a load carriage having upper rear roller means and lower front roller means movably engaging said outer upright, said inner upright unit having upper portions projecting forwardly relative to. the front face of said inner upright unitand other upper portions projecting rearwardly relativeto the: rear face of said inner upright unit, ancl'means' for elevatingsaid load carriage/along said outer upright and thereabove to place said roller meansuon said projecting portions, said elevating means being also operable to elevate said inner upright unit and said load carriageafte'r said roller means are in engagement withsaid projecting portion.

References Cited, in the file of-thispatent;

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